What does the ordinary detective of the St. Petersburg police Makar Aleksandrovich Gursky have to do! The search for a missing biologist who discovered a new powerful drug that can almost resurrect the dead unexpectedly leads to the Bolshevik organization. Guardians of the people's happiness began to engage in banal kidnappings in order to replenish the thinning party coffers. And when Grand Duke Alexander Mikhailovich, cousin of Nicholas II, turned to Gursky for help, the detective did not even imagine that he would be faced with an ancient secret - the brooch of the legendary Casanova, which supposedly has magical powers. properties.